Continuous roll wipe material dispenser

ABSTRACT

A continuous roll wipe material dispenser includes an upper module containing elements for mounting a rotatable roll of clean wipe material within the upper module and a lower module containing elements for receiving used wipe material within the lower module. The upper module is vertically spaced from the lower module thereby exposing between the modules a length of wipe material extending from the clean wipe material roll. The dispenser has a sensor element for detecting a user&#39;s hand approaching the exposed wipe material. A first driving element operates in response to the sensor element for dispensing a predetermined length of clean wipe material from the upper module. A second driving element operates in response to the dispensing of wipe material, in order to take up a predetermined length of used wipe material from between the modules each time a length of clean wipe material has been dispensed.

TECHNICAL FIELD

The present invention relates generally to continuous roll wipe materialor towel dispensers and, more particularly, to continuous roll toweldispensers adapted for automatic dispensing of clean wipe material froma supply roll contained in a separate module.

BACKGROUND ART

Conventional continuous roll towel dispensers will as a rule comprise awall mounted housing from which a stretched length or a loop of textiletowel is presented to a user. The user is required to grip the towel,preferably at both edges and pull a predetermined length of towel from asupply roll. After a predetermined time delay, which is selected to givethe user sufficient time to dry both hands, the length of used towel iswithdrawn by rolling it onto a used towel roll in the said housing.Often, the clean roll and the used roll are only separated by aninternal wall inside the housing.

One object of the present invention to provide an improved continuousroll towel dispenser which completely separates the clean towel rollfrom the used towel roll so that the clean towel cannot be contaminatedby the used towel. A related object of the invention is to provide suchan improved continuous roll towel dispenser which separates the cleantowel roll and the used towel roll and yet is relatively compact.

U.S. Pat. No. 3,574,431 discloses a modular dispenser with aconventional function, wherein the web material is presented to the useras a flat web and is pulled out manually from a first module by theuser. The used web is withdrawn automatically by a second module after apre-set time delay. This dispenser solves the problem of maintaining thesupply roll and used roll separated, but requires the user to withdrawthe towel. If a user pulls the towel excessively or attempts to withdrawan additional amount of towel, then the mechanism may be damaged. Also,if the towel is drawn out at an angle that does not coincide with thelongitudinal direction of the towel, then the towel may become bunchedup and block the feeding mechanism. In both cases, the dispenser willbecome inoperative until it can be serviced.

A further solution is disclosed DE 203 09 309, showing a modulardispenser where the supply roll and used roll are kept separated. Inthis case, the web is preferably arranged at right angles to the user.The dispenser is arranged to maintain the exposed length of towel in astretched position during use. When it is detected that the exposedlength of material has been used, a fresh length of material is fedforward. A problem with this dispenser is that the user may attempt towithdraw an additional length of towel, as this would be the commonprocedure for a standard continuous roll towel dispenser. Furthermore, auser may not feel comfortable with drying his/her hands on a flat,stretched length of material, which could also cause the user to try andwithdraw an additional length of towel. Again, an excessive forceapplied to the feeding mechanism may cause damage to the mechanism. Withthe towel presented to the user edge on, there is also a highprobability that the force will be applied at an angle and cause themechanism to malfunction, as described above.

Hence a further object of the invention is provide an improvedcontinuous roll towel dispenser which provides the user with asufficient length of towel while avoiding the risk of the mechanismbeing subjected to excessive force.

DISCLOSURE OF INVENTION

The above problems have been solved by a dispenser and a method forcontrolling said dispenser according to the appended claims.

According to a preferred embodiment, the invention relates to adispenser for a continuous roll of wipe material, which dispensercomprises the combination of an upper module containing means formounting a rotatable roll of wipe material within said upper module, alower module containing means for receiving used wipe material withinsaid lower module, said upper module being vertically spaced from thelower module so that a length of wipe material extending as asubstantially flat web from said clean wipe material roll is exposedbetween said modules. In the subsequent text, the term “dispenser” isused for the entire arrangement comprising at least an upper and a lowermodule.

The dispenser is provided with sensor means for detecting a user's handapproaching the exposed length of wipe material. The sensor means maycomprise one or more infra red (IR) sensors, radio frequency disruptionsensors, capacity sensors, motion or light detectors, photoelectriccells, proximity detectors or any other suitable type of contactlesssensor. Here, the term “sensor means” is used for a sensor arraycomprising at least one sensor unit. In order to ensure detection of anobject such as the hand(-s) of a user, the sensor means may comprisesensor units located at least along a lower edge, or similar, of theupper module. If it is desired to cover objects approaching the exposedwipe material from the sides of the upper module, additional sensorunits may be located at the lower end of the side surfaces of the uppermodule. A first driving means is arranged to be operated in responsiveto the sensor means for dispensing a predetermined length of wipematerial from said clean wipe material roll in said upper module. Thelength of material will form a loop suspended from the upper module andwill be sufficiently long to allow the user to grasp the wipe materialand dry both hands. A second driving means is arranged to be operated inresponse to the dispensing of wipe material, in order to take up apredetermined length of used wipe material from between the modules eachtime a length of clean wipe material has been dispensed from said cleanwipe material roll. The second driving means may be controlled by acontrol means to withdraw the used wipe material until a predeterminedresistance or tension is sensed or detected and the exposed length ofclean wipe material is stretched between the two modules. The length ofmaterial to be dispensed and withdrawn may be varied depending on thedistance between the dispensers and other parameters that may be set bythe supplier of the dispenser to achieve certain functions. Forinstance, for a dispenser having the modules mounted to provide anexposed length of 30-40 cm, the control means may actuate the firstdriving means to supply a user with 40 cm of clean wipe material. Whenthe user has wiped his hands, the second driving means will be actuatedto withdraw the used wipe material. In order to ensure that there is nooverlap of used section of wipe material, the first driving means may atthe same time be actuated to dispense a further 10-15 cm of clean wipematerial. The total length of wipe material used during each suchoperating cycle will then be 50-55 cm.

In order to control the operation of the dispenser it may be providedwith a control means interconnecting said first and second driving meansto automatically drive said second driving means to withdraw said lengthof used wipe material in response to operation of said first drivingmeans after the dispensing of wipe material from said clean wipematerial roll. The dispensing operation may be actuated when a handtriggers a sensor as the user reaches out to grasp the wipe material.The sensors may have a sensor field extending downwards and outwardsfrom at least the front of the upper module. As the hands of the usermay approach the edges of the wipe material from either side of thedispenser, the sensor field may also extend downwards and outwards fromthe sides of the upper module. The range of the sensor field ispreferably chosen so that the dispensing of clean wipe material isstarted before the user has gripped the side edges thereof. Withdrawalof the used length of material may be actuated after a predeterminedtime delay, where a counter may be triggered following the start or theend of the dispensing operation. Alternatively, the withdrawal functionmay be actuated when the sensors indicate that the hands of the userhave been removed out of the range of the sensor field of the at leastone sensor.

The lower module may contain means for mounting a rotatable roll forreceiving used wipe material, in which case the second driving meanswill act on the used roll. Alternatively, the second drive means may bearranged to draw the used wipe material into the lower module, whereafter the material is merely collected in the said module. The dispensermay use webs comprising tissue material, non-woven material and textilematerial. Examples of suitable materials are, for instance, a reinforcedtissue paper comprising a polymer net having outer plies of tissuepaper, or a web comprising a mixture of non-woven and tissue paper.

In order to allow the user to access the wipe material freely, the upperand lower modules may be arranged to space the exposed length of wipematerial a predetermined distance away from a common surface, such as awall. The modules are preferably mounted so that both side edges of theexposed length of wipe material are readily accessible to the user.Instead of being mounted directly on a wall or a similar surface, theupper and lower modules may be mounted on a common rear panel.

The upper module may be provided with an elongated wipe material egressslot or dispensing opening at a lower surface or a lower front corner ofthe module, which dispensing opening may extend along a major part ofthe width of the module. Similarly, the lower module may be providedwith an elongated wipe material ingress slot or opening at an uppersurface or an upper front corner of the lower module, so that theexposed length of wipe material between said egress and ingress slots ispresented substantially distanced from the module surfaces. In this waythe user may grasp the exposed length of wipe material without cominginto contact with either of the modules, an optional rear panelconnecting the modules or the wall surface onto which the dispensermodules are mounted.

In order to ensure that the length of dispensed wipe material forms aloop in front of and towards the user, the material ingress slot in thelower module should preferably, but not necessarily, be located behind avertical plane through the egress slot in the upper module. In this waythe vertical plane through the egress slot is located between theingress slot and the user. Hence, if the modules are mounted on avertical wall then the material ingress slot is preferably locatedcloser to the wall than the egress slot. The egress and ingress slot maybe allowed to be placed in the same vertical plane if the upper surfaceof the lower module is arranged angled downwards and outwards relativeto the wall. This arrangement would ensure that the weight of thedispensed wipe material causes the web to form a loop in front of andtowards the user. According to one example, the wipe material may extendfrom the lower front corner of the upper module towards the front cornerof the upper module. In this way the exposed wipe material may extend ina substantially vertical plane between the modules. According to afurther example, the wipe material may extend from the lower frontcorner of the upper module towards the upper surface of the lowermodule. In this way the exposed wipe material may extend in a planeangled inwards and downwards between the modules. Each of said upper andlower modules enclose said wipe material rolls and include an at leastpartially removable section for providing access to the respective rollof wipe material, that is to re-fill the upper module and empty thelower module.

According to a first alternative embodiment, the first driving meansincludes a pair of driven rollers in said upper module arranged tofrictionally engage said wipe material for dispensing a predeterminedlength thereof. According to a second alternative embodiment, the firstdriving means includes a driven roller in said upper module arranged tofrictionally engage said wipe material roll for dispensing apredetermined length thereof. According to a third alternativeembodiment, the first driving means includes a motor for driving theclean wipe material roll in said upper module for dispensing apredetermined length of said wipe material.

According to a fourth alternative embodiment, the second driving meansincludes a pair of rollers in said lower module arranged to frictionallyengage the used wipe material to withdraw the dispensed length of wipematerial into the second module. According to a fifth alternativeembodiment, the second driving means includes a driven roller in saidlower module arranged to frictionally engage the used wipe material rollto withdraw the dispensed length of wipe material into the secondmodule. According to a sixth alternative embodiment, the second drivingmeans includes a motor for driving the used wipe material roll forwinding the dispensed length of wipe material onto the used wipematerial roll in the second module. The above embodiments relating tothe second drive means may be combined with any one of the embodimentsrelating to the first drive means.

According to a further embodiment, the invention relates to a method forcontrolling a continuous roll wipe material dispenser as describedabove. The method may comprise the steps of

-   -   monitoring a first condition, indicating the presence of an        object approaching an exposed length of wipe material, and when        the first condition is fulfilled;    -   initiating a first drive means and dispensing a predetermined        length of wipe material from a first module,    -   monitoring a second condition, indicating the absence of the        user and/or the expiry of a predetermined period of time,        indicative of the wipe material having been used by a user, and        when the second condition is fulfilled;    -   initiating a second drive means and withdrawing the        predetermined length of wipe material into a second module.

The presence of an object approaching the exposed length of wipematerial may be determined by monitoring an output signal from a sensormeans, wherein the first condition is fulfilled when the said object isinside the range of the sensor means. Suitable sensor means for thispurpose and the arrangement of sensor units of such a sensor means havebeen described in the above text.

According to a first example, the condition indicative of the wipematerial having been used by a user may be determined by monitoring atime period after initiation of the first drive means. In this case, thesecond condition is fulfilled upon expiry of a predetermined period oftime.

According to a second example, the condition indicative of the wipematerial having been used by a user may be determined by monitoring anoutput signal from a sensor means, wherein the second condition isfulfilled when the said object is outside the range of the sensor means.This indicates the absence of the user. In order to ensure that the usedwipe material is withdrawn within a reasonable period of time, thisexample may be combined with the first example. This function may beused in case of a sensor malfunction, or if one or more sensors havebeen incapacitated or blocked. The period of time monitored in thesecond example may be the same or longer than that of the first example.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be described in detail with reference to the attachedfigures. It is to be understood that the drawings are designed solelyfor the purpose of illustration and are not intended as a definition ofthe limits of the invention, for which reference should be made to theappended claims. It should be further understood that the drawings arenot necessarily drawn to scale and that, unless otherwise indicated,they are merely intended to schematically illustrate the structures andprocedures described herein.

FIG. 1 shows a schematic illustration of a dispenser according to oneembodiment of the invention;

FIG. 2 shows a schematic illustration of according to an alternativeembodiment of the invention;

FIG. 3 shows a schematic illustration of according to an alternativeembodiment of the invention; and

FIG. 4 shows a schematic illustration of according to an alternativeembodiment of the invention.

EMBODIMENTS OF THE INVENTION

FIG. 1 shows a schematic illustration of a dispenser according to oneembodiment of the invention. The figure shows a dispenser comprisingcombination of an upper module A containing means for mounting arotatable roll of wipe material within said upper module A and a lowermodule B containing means for receiving used wipe material within thelower module B. The upper module A comprises a front cover 1, a pair ofside walls 2, 3, an upper section 4, a lower section 5 and a rearsection 6 (see FIG. 2), which rear section 6 is adapted for mounting ona wall or a similar surface. A dispenser opening 7 in the shape of anelongated slot is arranged along the lower, front portion of the uppermodule A, in an area where the front cover 1 joins the lower section 5.

Similarly, The lower module B comprises a front cover 11, a pair of sidewalls 12, 13, an upper section 14, a lower section 15 and a rear section16 (see FIG. 2), which rear section 16 is adapted for mounting on a wallor a similar surface below the upper module A. A receiving opening 17 inthe shape of an elongated slot is arranged along the upper, frontportion of the lower module B. The receiving opening 17 can be locatedin a substantially vertical plane between a substantially vertical planethrough the dispensing opening 7 and the rear section 16. The receivingopening 17 can be placed substantially directly below the dispensingopening 7, but is preferably located so that a length of wipe material Wextending between the openings is arranged at an angle downwards andinwards from the dispenser opening 7. The upper and lower modules A, Bcan be mounted directly on a wall or a similar surface, as shown in FIG.1, or be mounted on a common rear panel (see FIG. 2). Alternatively, aseparate spacing panel can be mounted on the wall between the upper andlower modules to ensure a desired spacing and to facilitate relativepositioning of the modules during mounting. Each of said upper and lowermodules enclose said wipe material rolls and include at least onepartially removable section for providing access to the respective rollof wipe material, that is to re-fill the upper module A and empty thelower module B.

The upper module A is vertically spaced from the lower module so that alength of wipe material W extending as a substantially flat web fromsaid clean wipe material roll is exposed between said modules. In orderto allow the user to access the wipe material freely, the upper andlower modules A, B are also arranged to space the exposed length of wipematerial W a predetermined distance away from the surface, such as awall, on which the modules are mounted. The modules are preferablymounted so that both side edges of the exposed length of wipe materialare readily accessible to the user.

The dispenser is provided with sensor means 18 for detecting a user'shand approaching the exposed length of wipe material W. The sensor means18 comprises at least one infra red (IR) sensor, or a similar suitabletype of contactless sensor. In order to ensure detection of an objectsuch as the hands of a user, the sensor means 18 comprises sensor unitslocated at least along a lower edge, or similar, of the upper module A(one only is indicated in FIG. 1). Additional sensor units 18, indicatedby dashed lines) can be located at the lower end of the side walls 2, 3of the upper module A to detect objects approaching the exposed wipematerial from the sides of the upper module A.

The operation of the dispenser will be described in detail in connectionwith the examples shown in the FIGS. 2-4 below. In all the examples,sensors in the upper module A of the dispenser are arranged to monitor afirst condition, indicating the presence of an object, such as a hand,approaching the exposed length of wipe material W. When the firstcondition is fulfilled, a first driving means is arranged to be operatedin responsive to the sensor means for dispensing a predetermined lengthof wipe material from said clean wipe material roll R1 in said uppermodule A. The length of material will form a loop L suspended from theupper module A and will be sufficiently long to allow the user to graspthe wipe material and dry both hands. A second driving means is arrangedto be operated in response to the dispensing of wipe material, in orderto take up a predetermined length of used wipe material from between themodules each time a length of clean wipe material has been dispensedfrom said clean wipe material roll R1.

For instance, for a dispenser having the modules mounted to provide anexposed length of 30-40 cm, the control means may actuate the firstdriving means to supply a user with 40 cm of clean wipe material. Whenthe user has wiped his hands, the second driving means will be actuatedto withdraw the used wipe material. In order to ensure that there is nooverlap of used section of wipe material, the first driving means may atthe same time be actuated to dispense a further 10-15 cm of clean wipematerial. The total length of wipe material used during each suchoperating cycle will then be 50-55 cm.

An electronic control means 27, 35, 47 is arranged to monitor a secondcondition, which condition is indicative of the wipe material havingbeen used by a user. According to a first example, the said secondcondition indicative of the wipe material having been used by a user maybe determined by monitoring a time period after initiation of the firstdrive means. In this case, the second condition is fulfilled upon expiryof a predetermined period of time. According to a second example, thesaid second condition indicative of the wipe material having been usedby a user may be determined by monitoring an output signal from a sensormeans 18, wherein the second condition is fulfilled when the said objectis outside the range of the sensor means 18.

The electronic control means interconnects said first and second drivingmeans, to automatically drive said second driving means to withdraw saidlength of used wipe material in response to operation of said firstdriving means after the dispensing of wipe material from said clean wipematerial roll. The dispensing operation may be actuated when a handtriggers a sensor as the user reaches out to grasp the wipe material.The sensors may have a sensor field extending downwards and outwardsfrom at least the front of the upper module A. As the hands of the usermay approach the edges of the wipe material from either side of thedispenser, the sensor field may also extend downwards and outwards fromthe sides of the upper module A. The range of the sensor field ispreferably chosen so that the dispensing of clean wipe material isstarted before the user has gripped the side edges thereof. Withdrawalof the used length of material may be actuated after a predeterminedtime delay, where a counter may be triggered to monitor a first timeperiod following the start of, or the end of, the dispensing operation.A suitable length of time for a first time period initiated at the startof the dispensing operating is approximately 5-10 seconds.

Alternatively, the withdrawal function may be actuated when the sensorsindicate that the hands of the user have been removed out of the rangeof the sensor field of the at least one sensor. In order to safeguardthat the wipe material is withdrawn, the withdrawal function may beactuated after a second period of time, which second time period isequal to or longer than the first period of time.

The lower module B may contain means for mounting a rotatable roll R2for receiving used wipe material, in which case the second driving meanswill act on the used roll. Alternatively, the second drive means may bearranged to draw the used wipe material into the lower module B, whereafter the material is merely collected in the said module. The dispensermay use both textile and non-woven webs of material.

According to a first alternative embodiment shown in FIG. 2, the firstdriving means 22 comprises a first pair of driven rollers 23, 24 in saidupper module A arranged to frictionally engage said wipe material fordispensing a length L thereof. The second driving means comprises asecond pair of driven rollers 25, 26 in said lower module B arranged tofrictionally engage the used wipe material to withdraw the dispensedlength L of wipe material into the lower module B.

According to a second alternative embodiment, the first driving means 31comprises a first driven roller 33 in said upper module A arranged tofrictionally engage said wipe material roll for dispensing a length Lthereof. The second driving means 32 comprises a second driven roller 34in said lower module B arranged to frictionally engage the used wipematerial roll to withdraw the dispensed length of wipe material into thelower module.

According to a third alternative embodiment, the first driving means 41comprises a motor 43 for driving the clean wipe material roll R1 in saidupper module A for dispensing a length of said wipe material. The seconddriving 42 means comprises a motor 44 for driving the used wipe materialroll R2 for winding the dispensed length of wipe material L onto theused wipe material roll R2 in the lower module B.

The above alternative embodiments relating to the second drive means maybe combined with any one of the embodiments relating to the first drivemeans.

The invention is not limited to the above examples, but may be variedfreely within the scope of the appended claims.

1. A continuous roll wipe material dispenser comprising the combinationof an upper module containing means for mounting a rotatable roll ofwipe material within said upper module, a lower module containing meansfor receiving used wipe material within said lower module, said uppermodule being vertically spaced from the lower module so that a length ofwipe material extending from said clean wipe material roll is exposedbetween said modules, wherein the dispenser is provided with sensormeans for detecting a user's hand approaching the exposed wipe material;a first driving means arranged to be operated in responsive to thesensor means for dispensing a predetermined length of wipe material fromsaid clean wipe material roll in said upper module; and a second drivingmeans arranged to be operated in response to the dispensing of wipematerial, in order to take up a predetermined length of used wipematerial from between the modules each time a length of clean wipematerial has been dispensed from said clean wipe material roll.
 2. Thecontinuous roll wipe material dispenser according to claim 1, whereinthe lower module contains means for mounting a rotatable roll forreceiving used wipe material.
 3. The continuous roll wipe materialdispenser according to claim 1, wherein the second driving means isarranged to be operated after a predetermined period of time after thedispensing of wipe material from said clean wipe material roll.
 4. Thecontinuous roll wipe material dispenser according to claim 1, whereinsaid upper and lower modules are arranged to space the exposed length ofwipe material a predetermined distance away from a common surface onwhich said modules are mounted so that both side edges of the exposedlength of wipe material are readily accessible to the user.
 5. Thecontinuous roll wipe material dispenser according to claim 4, whereinsaid upper and lower modules are mounted on a common rear panel.
 6. Thecontinuous roll wipe material dispenser according to claim 4, whereinsaid upper and lower modules are mounted as separate units on a wallsurface.
 7. The continuous roll wipe material dispenser according toclaim 1, wherein each of said upper and lower modules enclose said wipematerial rolls and include an at least partially removable section forproviding access to the wipe material rolls contained therein.
 8. Thecontinuous roll wipe material dispenser according to claim 1, whereinsaid upper module comprises an elongated wipe material egress slot atthe lower front corner thereof and said lower module comprises anelongated wipe material ingress slot at the upper front corner thereofso that the exposed length of wipe material between said egress andingress slots is substantially distanced from the module surfaces. 9.The continuous roll wipe material dispenser according to claim 1,wherein said lower module comprises an elongated wipe material ingressslot and said upper module comprises an elongated wipe material egressslot, and where a vertical plane through the egress slot is locatedbetween the ingress slot and the user.
 10. The continuous roll wipematerial dispenser according to any claim 1, wherein said first drivingmeans includes a pair of driven rollers in said upper module arranged tofrictionally engage said wipe material for dispensing a predeterminedlength thereof.
 11. The continuous roll wipe material dispenseraccording to claim 1, wherein said first driving means includes a drivenroller in said upper module arranged to frictionally engage said wipematerial roll for dispensing a predetermined length thereof.
 12. Thecontinuous roll wipe material dispenser according to claim 1, whereinsaid first driving means includes a motor for driving the clean wipematerial roll in said upper module for dispensing a predetermined lengthof said wipe material.
 13. The continuous roll wipe material dispenseraccording to claim 10, wherein said second driving means includes a pairof rollers in said lower module arranged to frictionally engage the usedwipe material to withdraw the dispensed length of wipe material into thesecond module.
 14. The continuous roll wipe material dispenser accordingto claim 9, wherein said second driving means includes a driven rollerin said lower module arranged to frictionally engage the used wipematerial roll to withdraw the dispensed length of wipe material into thesecond module.
 15. The continuous roll wipe material dispenser accordingto claim 9, wherein said second driving means includes a motor fordriving the used wipe material roll for winding the dispensed length ofwipe material onto the used wipe material roll in the second module. 16.The continuous roll wipe material dispenser according to claim 1,wherein the dispenser is provided with control means interconnectingsaid first and second driving means to automatically drive said seconddriving means to withdraw said used wipe material roll in response tooperation of said first driving means after the dispensing of wipematerial from said clean wipe material roll.
 17. The continuous rollwipe material dispenser according to claim 1, wherein the sensor is acontactless sensor.
 18. The continuous roll wipe material dispenseraccording to claim 17, wherein the sensor is an infrared sensor.
 19. Thecontinuous roll wipe material dispenser according to claim 17, whereinthe sensor is an inductive sensor.
 20. Method for controlling acontinuous roll wipe material dispenser according to claim 1, comprisingthe steps of monitoring a first condition, indicating the presence of anobject approaching an exposed length of wipe material, and when thefirst condition is fulfilled; initiating a first drive means anddispensing a predetermined length of wipe material from a first module,monitoring a second condition, indicating the absence of the user and/orthe expiry of a predetermined period of time, and when the secondcondition is fulfilled; and initiating a second drive means andwithdrawing the predetermined length of wipe material into a secondmodule.
 21. Method according to claim 20, further comprising monitoringan output signal from a sensor means, wherein the first condition isfulfilled when the object is inside the range of the sensor means. 22.Method according to claim 20, further comprising monitoring a timeperiod after initiation of the first drive means, wherein the secondcondition is fulfilled upon expiry of a predetermined first period oftime.
 23. Method according to claim 20, further comprising monitoring anoutput signal from a sensor means, wherein the second condition isfulfilled when the object is outside the range of the sensor means. 24.Method according to claim 23, further comprising monitoring a timeperiod after initiation of the first drive means, wherein the secondcondition is fulfilled upon expiry of a predetermined second period oftime, which second time period is equal to or longer than the firstperiod of time.